This invention relates to a thermoplastic resin-coated aluminum plate and articles formed from the same. More specifically, it relates to a thermoplastic resin-coated aluminum plate which is less liable to defect such as ply separation when subjected to drawing, ironing or caulking, ply separation with time, and peeling of the coating film if subjected to heat treatment after working, and which is superior in working adhesion and heat-resistant adhesion after working, and to an article formed from such a thermoplastic resin-coated aluminum plate.
Resin-coated metallic plates which have a thermoplastic resin coating film laminated on an aluminum or aluminum alloy plate are used in various fields, making the most of their excellent properties such as workability, corrosion resistance and electrical insulation e.g. for casings of electrolytic aluminum capacitors. In these applications, since such resin-coated metallic plates are formed into end articles, it is required that no peeling, crack or breakage develop in the thermoplastic resin coating film during the forming step. In order to meet these requirements and to obtain thermoplastic resin-coated metallic plates superior in working adhesion, various trials have been made.
For example, there have been proposed a method in which a film of an epoxy resin having a surface analysis spectrum value measured by an X-ray electron spectroscopy below a predetermined value is provided on the surface of a metallic material as a substrate film and a polyamide film is laminated on this film (Japanese patent publication 1-238931), a method in which a coating comprising a fatty acid or hydroxymethyl-substituted phenol is formed as a substrate film on the surface of a metallic material, the coating is subjected to heat treatment at a temperature of 350xc2x0 C. or above to form a heat-modified film, and a polyamide resin film is laminated on the film (Japanese patent publication 3-2036), and a method in which a polyamide resin having a diffraction strength within a predetermined range by X-ray diffraction is laminated on a metallic plate by melt extrusion (Japanese patent publication 11-245330).
Polyamide resin-coated metallic plates manufactured by such methods are less liable to peeling at worked portions in the drawing step, but the adhesion strength at the worked portions lowers as time passes. Thus, in order to prevent the adhesion strength from lowering with time, as proposed in Japanese patent publications 1-66030 and 2-18043, it is necessary to re-melt the film by further heat treatment after forming such as drawing.
Under such circumstances, in an attempt to solve all the above problems, the present inventors have completed the present invention.
1. An object of the present invention is to provide a thermoplastic resin-coated aluminum plate which when it is subjected to ironing or drawing, is less liable to ply separation or crack in the coated resin layer or film, or peeling of the resin coating film off the aluminum plate.
2. Another object is to provide a thermoplastic resin-coated aluminum plate in which even after time has passed after working, the adhesion strength at the worked portions will not lower, and heat treatment after forming is not needed, and which is superior in working adhesion and adhesion after working.
3. A further object is to provide a formed article made from such a thermoplastic resin-coated aluminum plate.
According to the first invention of the present invention, there is provided a thermoplastic resin-coated aluminum plate comprising a semi-non-porous anodized film formed on at least one side of an aluminum plate, a coating layer formed on the semi-non-porous anodized film, and a thermoplastic resin coating film formed on the coating layer.
According to the second invention of the present invention, there is also provided a formed article made from a thermoplastic resin-coated aluminum plate, which is formed by working the thermoplastic resin-coated aluminum plate.